A primary example of non-invasive methods for diagnosing arteriosclerosis includes X-ray angiography. This method involves contrasting vascular flows by using a water-soluble iodine-containing contrast medium, and for this reason, the method has a problem of poor distinguishability of pathological tissues from normal tissues. The above method only achieves detection of a lesion where constriction progresses 50% or more, and the method has difficulty in detecting a lesion before onset of attack of an ischemic disease.
As diagnostic methods other than the above, methods of detecting a disease by nuclear magnetic resonance tomography (MRI) have been reported in recent years which use a contrast medium kinetically distributed at a high level in arteriosclerotic plaques. However, any of compounds reported as the contrast medium has a problem when used in diagnostic methods. For example, hematoporphyrin derivatives are reported to have a defect of deposition in the skin and coloring of the skin (see, U.S. Pat. No. 4,577,636 the disclosure of which is expressly incorporated by reference herein in its entirety). As for gadolinium complexes having a perfluorinated side chain which have been reported to accumulate in lipid-rich plaques, accumulation in lipid-rich tissues and organs in vivo, such as fatty livers, renal epitheliums, and tendons of muscular tissues is of concern (see, Circulation, 109, 2890, 2004, the disclosure of which is expressly incorporated by reference herein in its entirety).
From a viewpoint of chemical compounds, a steroid ester of fatty acid wherein all the hydrogen atoms other than those at α-position are substituted with fluorine atoms is known (Tetrahedron, 45, 6467, 1989, the disclosure of which is expressly incorporated by reference herein in its entirety). However, the steroid ester is disclosed in the publication in relation of fluorination by a photoreaction, and its application for a contrast medium is not known.
Alcohol esters having structures of bis(trifluoromethyl)benzoic acid and steroid skeleton are also known. However, these esters have a sterically-hindered structure near the ester group and thus a low degradability in vivo is of concern.
Phosphatidylcholine type compounds with a fluorinated alkyl group (see, for example, Langmuir, 19, 4889, 2003, the disclosure of which is expressly incorporated by reference herein in its entirety) are known. However, phosphatidylserine type compounds are not known.
Further, a compound is known wherein a carboxylic acid having polyaminoethylene residue binds to a diglyceride with a fluorinated alkyl group (see, for example, WO9834910, the disclosure of which is expressly incorporated by reference herein in its entirety). However, a compound having polyamine structure is susceptible to be positively charged. Therefore, generation of toxicity in vivo through interaction with a cell membrane and DNA is of concern.